The interaction of an electromagnetic field with the enzymatic substrate-- the sodium salt of fructose-1,6-disphosphate--induces in the latter a new type of physical transition S leads to S. The enzyme, in this case Saccharomyces cerevisiae aldolase, is able to reveal this new state of the substrate by an increase in its specific activity within well established irradiation times. Each enzyme is characterized by the tm (minimal irradiation time of the substrate) a tau (fixed time period) parameters that delimit the two signals. Purified S. cerevisiae aldolase has tm=5 sec. and tau=20 sec., in contrast to muscle aldolase (represented by class I aldolase) which has tm=15 sec. and tau=30 sec. This may be attributed to the fact that most of the enzymatic systems in S. cerevisiae are made up of several distinct molecular forms, involved in more metabolic pathways than in the animal tissue, therefore with various responses to the phenomenon of perturbation of the substrates.